Bullous Pemphigoid (BP) and herpes gestationis (HG) are life-threatening blistering diseases that are characterized by the production of autoantibodies directed against the hemidesmosomal proteins, BPl80 and BP230, and by itie formation of subepidermal vesicles. The overall goal of this project is to advance our understanding of the immunopathological mechanisms operating in these diseases. The major focus of the present proposal is to test the hypothesis that the destruction of the dermal-epidermal junction is caused by proleolytic enzymes released from infiltrating inflammatory cells. Specific aims 1 and 2 are to further dissect the mechanism of recruitment and activation of neutrophils (i.e. the role of cell adhesion molecules and cell surface receptors) and investigate the possible role of eosinophils in subepidermal blistering. Passive transfer experiments with pathogenic anti-BP180 IgG will be performed on mice deficient in proinflammatory cytokines, neutrophil migration-related integrins or activation-related Fc receptors. The role of eosinophils will be investigated by depletion and reconstitution experiments. Specific aim 3 is designed to determine the role of proteolytic enzymes and the reactive oxidants in experimental BP and HG and test the hypothesis that degradation products of BPl80 are chemotactic. Mice deficient in these proteinases will be injected with pathogenic IgG. The chemotactic activity of the BPl80 fragments will be tested by in vitro and in vivo chemotaxis assays. Specific aim 4 is to study effects and mechanisms of action of anti-inflammatory drugs in subepidermal blistering using passive transfer experiments and pharmacologic approaches. Specific aim 5 is to develop a novel system to directly test the pathogenic activity of autoantibodies from BP and HG patients' sera. These autoantibodies will be injected into neonatal transgenic mice expressing human BPl80 in the basal keratinocytes. Affinity-purified autoantibodies against specific antigenic sites on human BPl80 will also be used in this in viva system to map the pathogenic epitopes). The results from these studies will have profound clinical implications in the care of patients with BP and HG and other related diseases.